Such a catheter, known from EP-A-0 688 580, is intended for use after a recanalization treatment in which a substantially occluded blood vessel (for example as a result of the depositing of so-called plaque within the lumen of the blood vessel) is stretched by means of an expandable element, such as a fluid-inflatable recanalization balloon, fastened to the distal end of an elongated catheter tube, in order to permit the blood to flow unimpeded again through the stretched blood vessel.
It is frequently found after a relatively short period of time that a new recanalization treatment is necessary because a constriction is again forming in the blood vessel or has already formed. That constriction may be a consequence of tissue developing at the stretched place (known as neointima proliferation), probably due to the fact that the wall of the blood vessel is damaged by the stretching. This formation of tissue can be prevented to a large extent or at least reduced if, during or shortly after the recanalization treatment, the blood-vessel tissue in question is irradiated with ionizing radiation, in particular .beta. and/or .gamma. radiation.
For such a treatment, the catheter known from EP-A-0 668 580 can be used. The intensity of radiation of the radioactive element introduced decreases greatly with the distance. In order not to permit the radiation dose to be too great (damaging of vessel wall) or too low (not the intended reduction of tissue developing at the stretched place), it is important to center the radioactive element accurately in the blood vessel. This is done in the known catheter by centering means in the form of an inflatable balloon which is subdivided by constriction means into a plurality of balloon parts. The constriction means are so dimensioned that the different balloon parts communicate with each other.
Upon such a treatment, therefore, the recanalization catheter must first of all be brought to the desired place and, after the carrying out of the recanalization treatment, be removed and replaced by the catheter for the guiding of the radioactive element, in which connection, of course, great care must be paid to the fact that the radioactive element must be placed precisely at the place of the earlier recanalization treatment. All in all, this is a cumbersome and timeconsuming method which must be carried out with extreme caution, while, also from the standpoint of the patient who must undergo the treatment, it is preferable for it to be carried out as rapidly and efficiently as possible.
The object of the invention then is the provision of such an instrument that the treatment can be carried out in a short time and effectively and reliably with as few manipulations as possible.